Prostate diseases represent a significant health problem in the United States. After cardiac diseases and lung cancer, metastatic prostate cancer is the third leading cause of death among the American men over fifty years, resulting in approximately 31,000 deaths annually. The definitive diagnostic method of prostate cancer is core needle biopsy. Annually in the U.S., approximately 1 million prostate biopsies are performed. The average number of new prostate cancer patients detected by needle biopsy has stabilized around 200,000 per year. Due to the evolution in screening techniques, more cases are diagnosed at an earlier stage, when patients are candidates for some form of minimally invasive localized therapy typically delivered with needles. The majority of the cancer-free biopsied patients are likely to have benign prostate hyperplasia (BPH). Currently more than 10 million American men suffer from BPH. Significant attention has been focused on minimally invasive local therapies of this condition, because its definitive treatment, transurethral resection (TURP) is a highly invasive surgical procedure with potentially adverse side effects. Needle-based ablative therapies have shown promising results lately in the treatment of BPH.
Currently, transrectal ultrasound (TRUS) guided needle biopsy is primary technique being utilized for the diagnosis of prostate cancer [Presti J C Jr. Prostate cancer: assessment of risk using digital rectal examination, tumor grade, prostate-specific antigen, and systematic biopsy. Radiol Clin North Am. 2000 January; 38(1):49-58. Review] and contemporary intraprostatic delivery of therapeutics is also primarily performed under TRUS guidance. This technique has been overwhelmingly popular due to its excellent specificity, real-time nature, low cost, and apparent simplicity. At the same time, however, TRUS-guided biopsy fails to correctly detect the presence of prostate cancer in approximately 20% of cases [Norberg M, Egevad L, Holmberg L, Sparen P, Norlen B J, Busch C. The conventional sextant protocol for ultrasound-guided core biopsies of the prostate underestimates the presence of cancer. Urology. 1997 October; 50(4):562-6; Wefer A E, Hricak H, Vigneron D B, Coakley F V, Lu Y, Wefer J, Mueller-Lisse U, Carroll P R, Kurhanewicz J. Sextant localization of prostate cancer: comparison of sextant biopsy, magnetic resonance imaging and magnetic resonance spectroscopic imaging with step section histology. J Urol. 2000 August; 164(2):400-4].
For the same reason, targeted local therapy today also is not possible with the use of TRUS guidance. Instead, major anatomical regions (or most often the entire prostate gland) are treated uniformly while trying to maintain the fragile balance between minimizing toxic side effects in surrounding normal tissues and providing/giving a sufficient therapeutic dose to the actual cancer. Also importantly, the transrectal ultrasound probe applies variable normal force on the prostate through the rectal wall, causing dynamically changing deformation and dislocation of the prostate and surrounding tissue during imaging and needle insertion, an issue that has to be eliminated in order to achieve accurate and predictable needle placement. The key to successful prostate biopsy and local therapy is accurate, consistent and predictable needle placement into the prostate, and some form of image guidance.
MRI imaging has a high sensitivity for detecting prostate tumors. Unfortunately, MR imaging alone, without concurrent biopsy, suffers from low diagnostic specificity. In addition, there are other fundamental obstacles that must be addressed when using MRI imaging techniques in prostate biopsy and related localized therapy of the prostate. Conventional high-field MRI scanners use whole-body magnets that surround the patient completely and do not allow access to the patients during imaging. Thus, the workspace inside the bore of the whole-body magnet is so extremely limited, that conventional medical robots and mechanical linkages do not fit inside the whole-body magnet. Also, the strength of the magnetic field being generated within the whole-body magnet is about 200,000 times stronger than the magnetic field of the earth. Due to these ultra-strong magnetic fields, ferromagnetic materials and electronic devices are not allowed to be in the magnet due to safety and/or imaging concerns, which excludes the use of traditional electro-mechanical robots and mechanical linkages.
Tempany, D'Amico, et al. [Cormack R A, D'Amico A V, Hata N, Silverman S, Weinstein M, Tempany C M. Feasibility of transperineal prostate biopsy under interventional magnetic resonance guidance. Urology. 2000 Oct. 1; 56(4):663-4; D'Amico A V, Tempany C M, Cormack R, Hata N, Jinzaki M, Tuncali K, Weinstein M, Richie J P. Transperineal magnetic resonance image guided prostate biopsy. J Urol. 2000 August; 164(2):385-7'] proposed to use an open MRI configuration in order to overcome spatial limitations of the scanner. The magnet configuration for this open MRI configuration allows the physician to step inside the magnet and deliver biopsy and therapeutic needles into the prostate. This approach showed that it was possible to use an MRI imaging process to detect cancer previously missed by ultrasound guided needle biopsy and to perform targeted brachytherapy of the prostate. This technique has limitations, however, because it involves the use of an open MRI scanner. Perhaps most importantly, the incurred cost and complexity of open MRI imaging are substantial, especially when compared to transrectal ultrasound imaging.
Open magnets also tend to have weaker magnetic fields than the magnetic fields that are generated using closed magnets, thus open magnets tend to have lower signal-to-noise ratio (SNR) than the SNR for a closed high-field MRI scanners. Consequently, intra-operative images for an open magnet tend to be of a lower quality than the diagnostic images from a closed MRI scanner. While this approach seems to be acceptable when used in a research type of environment, it adds to the complexity and cost of the open MRI. Tempany et al. apply transperineal needle placement for both biopsy and brachytherapy, which is conventionally accepted for therapy, but for biopsy, it is a significantly more invasive route than through the rectum.
Traditionally, needles are placed into the prostate manually while observing some intra-operative guiding images, typically real-time transrectal ultrasound. TRUS biopsy is executed with entirely free hand. Transperineal needle placement is significantly more controlled by stepping transrectal ultrasound and template jigs, however, it still depends on the physician's hand-eye coordination. Therefore, the outcomes of TRUS guided procedures show significant variability among practitioners.
Recently, a 6-DOF robot has been presented for transperineal needle placement into the prostate, but that kinematic concept is not applicable in transrectal procedures [G. Fichtinger, T. L DeWeese, A. Patriciu, A. Tanacs, D. Mazilu, J. H. Anderson, K. Masamune, R H. Taylor, D. Stoianovici: Robotically Assisted Prostate Biopsy And Therapy With Intra-Operative CT Guidance: Journal of Academic Radiology, Vol 9, No 1, pp. 60-74]. An industrial robot also has been applied to assist TRUS-guided prostate biopsy with the use of a conventional end-shooting probe [Rovetta A, Sala R: Execution of robot-assisted biopsies within the clinical context, Journal of Image Guided Surgery. 1995; 1(5):280-287]. In this application, the robot mimicked the manual handling of TRUS biopsy device in the patient's rectum, in a telesurgery scenario.
A robotic manipulator has been reported for use inside an open MRI configuration, which device is intended to augment the Tempany et al. developed system [Chinzei K, Hata N, Jolesz F A, Kikinis R, M R Compatible Surgical Robot: System Integration and Preliminary feasibility study, Medical Image Computing and Computer-assisted Intervention 2000, Pittsburgh, Pa. Lecture Notes in Computer Science, MICCAI 2000, Springer-Verlag, Vol. 1935, pp. 921-930]. The motors of this robot are situated outside the first magnetic zone, while the motors actuate two long arms to manipulate the surgical instrument in the field of imaging. This solution is not suitable for a closed magnet configuration. In addition, the long arms of this robotic manipulator amplify the effects of flexure and sagging, which can render this system inaccurate for certain procedures. Moreover, because the device is intended to be mounted permanently with respect to the MRI scanner, the robotic manipulator is not flexibly adaptable to different sides of the body.
Recently, a robot has been developed for use inside a conventional MRI scanner that is custom-designed for breast biopsy, [Kaiser W A, Fischer 14, Vaguer J, Selig M. Robotic system for biopsy and therapy of breast lesions in a high-field whole-body magnetic resonance tomography unit. Invest Radiol. 2000 August; 35(8):513-9]. This robot is mounted on the table of the scanner and it realized six degrees of freedom (6 DOF). This robot is demonstrated in accessing the breast, but it is not readily adaptable for abdominal and intracavity use. There also has been published variations of an in-MRI robot for stereotactic brain surgery, but the actual embodiments of that system also are not applicable in transrectal biopsy [Masamune et. al., Development of an MRI-compatible needle insertion manipulator for stereotactic neurosurgery. Journal of Image Guided Surgery, 1995, 1 (4), pp. 242-248].
The development of magnetic resonance imaging (MRI) guided robotic intervention instruments also necessarily involves and is complicated by the need to track in real-time the position and orientation of these instruments within the MRI scanner. Consequently a variety of methods have been developed for the spatial registration and tracking of robotic and manual instruments within MRI scanners. The reported approaches include joint encoding, passive fiducial features, optical position sensing, gradient field sensing and micro-tracking sensing coils.
As is known to those skilled in the art, in the joint encoding approach the position of the intervention device (e.g., needle or other surgical device) is determined by joint encoders. This approach has its limitations in that it requires or involves the addition of a rigid mechanical mounting system to the MRI scanner so the intervention device is mounted rigidly on the MRI scanner, in a highly repeatable manner and also requires a precise pre-calibration of the device with respect to the scanner coordinate system before using the interventional device.
A number of systems or methods have been developed around the use of passive MRI fiducials that are attached or registered to the intervention device in a pre-set geometric arrangement. As is known to those in the art, the fiducials include materials that are visible or detectable during the MRI process. In one reported system, template holes of a passive needle guiding template for transperineal MRI-guided HDR prostate brachytherapy were filled with a contrast material, which were pre-operatively localized in standard T1 or T2-weighted images and registered to the coordinate frame of the MRI scanner. In a reported MRI guided transrectal needle biopsy system a passive fiducial marker sleeve coaxial with the biopsy needle was employed. In this system, the needle position is manually adjusted while the passive marker is imaged with oblique T2-weighted turbo spin echo (TSE) image sequences. While this approach is based on the use of inexpensive and robust passive fiducials, the approach does require or involve repeated volume imaging of high resolution that takes considerable time to acquire.
The optical position sensing approach involves an optical tracking system that is deployed and calibrated with respect to the scanner coordinate system. Such a system also requires line-of-sight between the optical tracking cameras and the device, and requires tethered light-emitting diodes (LEDs) to be attached to the instrument. Although this approach provides real-time tracking performance suitable for visual serving, the line-of-sight requirement of such a system renders this approach from unusable with conventional closed-bore MRI scanners.
In the gradient field sensing approach, the gradient field and conventional pulse sequences are used for localization. In regards to this approach, Hushek et al. investigated an FDA-approved commercial tracking mechanism called EndoScout (Robin Medical Systems, Baltimore, Md.) in the open MRI scanner (the device utilizes conventional image pulse sequences and gradient field for localization). In present implementations, however, the tracking sensors must be placed close to the MRI magnet's isocenter, and thus may occupy critical volume in the interventional device. This approach also requires a precise one time calibration procedure to be performed over the entire field of interest in each MRI system on which it is installed.
Another of the previously reported tracking methods employs a number of micro-tracking coils (e.g., three or more micro-tracking coils) that are rigidly attached to an MRI-compatible instrument. In this approach, a series of custom-programmed MRI pulse sequences provide one dimensional projections of the coil positions for each coil. Each individual projection pulse sequence takes several milliseconds, and the Cartesian position of all three micro-tacking coils can be completed within 50 ms. The individual micro-coil position data are employed to compute the six degree-of-freedom (6-DOF) position and orientation of the instrument with respect to the scanner coordinate system. Update rates of 20 Hz for full 6-DOF tracking have been reported. While the micro-coil tracking approach advantageously yields high accuracy (e.g., mean positional errors of 0.2 mm and 0.3 degrees), high speed (full 6-DOF tracking update rates of 20 Hz have been reported) and direct real-time 6-DOF tracking of the tool end-point, there are some shortcomings.
The use of micro-coils for tracking involves the development of custom tracking pulse sequences which necessarily must be implemented, and tested for each scanner. These pulse sequences differ from the standard imaging pulse sequences normally available on MRI scanners. Also, few scanners presently support micro-coil tracking as a standard capability. In addition a custom interface between the scanner software and a tracking program must be established to access the tracking coil locations.
Also, the tracking coils require a minimum of three scanner receiver channels. Most present-day MRI scanners posses four or more receiver channels, thus this method can be used on most scanners, however this does limits the number of imaging coils that can be used simultaneously for an interventional procedure. Further, this approach requires a minimum of three micro-coils to be incorporated within the navigated instrument. This can complicate the design and manufacturing of the instrument. Moreover, the micro-coils normally require a custom-built tuning, detuning and impedance matching circuit to be developed for each scanner. Based on experience the frequent failures in the micro-coils and electrical circuit significantly degrades the reliability of the overall MRI guided instrument.
It thus would be desirable to provide a new device, apparatus, systems and methods for image-guided biopsy and/or a wide range of therapeutic techniques including needle therapy that employs high resolution MRI imaging inside a closed MRI scanner. It also would be particularly desirable to provide such devices, apparatuses, systems and methods for image guided biopsy and/or therapeutic techniques of the prostate, rectum, vagina or cervix, as well as an artificial opening created in the body such as for example those used in connection with laparoscopic procedures/techniques. It would be particularly desirable to provide such a device, apparatus, system and method that would replace the conventional manual technique with a controlled needle insertion and guiding technique to maximize needle placement accuracy and also to minimize dynamic tissue deformation during the procedure. It also would be particularly desirable to provide such devices, apparatuses, systems and methods that employ real-time MRI guidance, are compatible with conventional high-field MRI scanners with no artifact, that can fit inside a closed whole-body magnet, that can perform needle insertion (e.g., transrectal needle insertion), that minimizes organ motion and deformation in a non-invasive manner and which provides three degree-of-freedom motion to reach a target within the body and selected by the user/medical personnel. It also would be particularly desirable to provide devices, apparatuses, systems and methods that embody a tracking methodology having an accuracy comparable to the accuracy for active tracking coils, but which does not require the use of such active tracking coils.